Vitamin K and metabolic bone disease

Vitamin K and cystic fibrosis: A gordian knot that deserves our attention

Cystic fibrosis (CF) is an inherited genetic disorder with multiorgan involvement. Gastrointestinal tract dysfunction leads to fat and fat-soluble vitamins (A,D,E,K) malabsorption and deficiency of these vitamins. Subclinical vitamin K (VK) deficiency seems to be a common problem in CF patients. However, despite the rest of fat-soluble vitamins being routinely supplemented, this is not a universal clinical practice for VK. Inefficient levels of VK may have significant effects on blood coagulation and bone formation. There are also some data indicating that VK may play a key role on regulation of inflammation. Supplementing CF patients with VK seems rational, but the appropriate dosing regimens are still a matter of debate. This review will try to delineate the problem and communicate the latest opinions on this controversial issue.

Bone Health and Osteoporosis: The Role of Vitamin K and Potential Antagonism by Anticoagulants

BACKGROUND

Vitamin K's effects extend beyond blood clotting to include a role in bone metabolism and potential protection against osteoporosis. Vitamin K is required for the gamma-carboxylation of osteocalcin. Likewise, this gamma-carboxylation also occurs in the liver for several coagulation proteins. This mechanism is interrupted by coumarin-based anticoagulants in both the liver and bone.

METHODS

A thorough review of the literature on vitamin K, osteocalcin and their role in bone metabolism and osteoporosis, as well as the potential bone effects of anticoagulant therapy was conducted.

CONCLUSIONS

Epidemiological studies and clinical trials consistently indicate that vitamin K has a positive effect on bone mineral density and decreases fracture risk. Typical dietary intakes of vitamin K are below the levels associated with better BMD and reduced fracture risk; thus issues of increasing dietary intakes, supplementation, and/or fortification arise. To effectively address these issues, large-scale, intervention trials of vitamin K are needed. The effects of coumarin-based anticoagulants on bone health are more ambiguous, with retrospective studies suggesting that long-term therapy adversely affects vertebral BMD and fracture risk. Anticoagulants that do not affect vitamin K metabolism are now available and make clinical trials feasible to answer the question of whether coumarins adversely affect bone. The research suggests that at a minimum, clinicians should carefully assess anticoagulated patients for osteoporosis risk, monitor BMD, and refer them to dietitians for dietary and supplement advice on bone health. Further research is needed to make more efficacious decisions about vitamin K intake, anticoagulant therapy, and bone health.

Menaquinones, bacteria, and the food supply: the relevance of dairy and fermented food products to vitamin K requirements

Vitamin K exists in the food supply as phylloquinone, a plant-based form and as menaquinones (MKs), a collection of isoprenologues mostly originating from bacterial synthesis. Although multiple bacterial species used as starter cultures for food fermentations synthesize MK, relatively little is known about the presence and distribution of MK in the food supply and the relative contribution of MK to total dietary vitamin K intake. Dairy products may be a predominant source of dietary MK in many regions of the world, and there is recent interest in enhancing the MK content of dairy products through identification and selection of MK-producing bacteria in dairy fermentations. This interest is increased by emerging evidence that current dietary recommendations based on the classic role of vitamin K as an enzyme cofactor for coagulation proteins may not be optimal for supporting vitamin K requirements in extrahepatic tissues and that MK may have unique bioactivity beyond that as an enzyme cofactor. Observational studies have reported favorable associations between MK intake and bone and cardiovascular health. Although randomized trials have provided some evidence to support the beneficial effects of MK on bone, the evidence to date is not definitive, and randomized trials have not yet examined MK intake in relation to cardiovascular outcomes. Food production practices provide a means to enhance dietary MK availability and intake. However, parallel research is needed to optimize these production practices, develop comprehensive food MK content databases, and test hypotheses of unique beneficial physiological roles of MK beyond that achieved by phylloquinone.

The prevalence of fat-soluble vitamin deficiencies and a decreased bone mass in patients with chronic pancreatitis

BACKGROUND/OBJECTIVES

In chronic pancreatitis, malabsorption of fat is common due to loss of exocrine function. Consequently, these patients are at risk to acquire deficiencies of the fat-soluble vitamins, which may result in a decreased bone mineral density (BMD) and the development of osteopenia and osteoporosis.

METHODS

We prospectively enrolled all patients diagnosed with chronic pancreatitis, who visited our outpatient clinic between March and November 2011. Data were collected regarding demographic characteristics, symptoms, and pancreatic function. Serum concentrations of vitamins A, E, K, and D were determined, and BMD was assessed by means of bone densitometry. Results were analyzed according to pancreatic function status and enzyme use, and compared to reference data, when available.

RESULTS

Forty patients were included (43% female; mean age of 52). Alcohol abuse was the major cause of pancreatitis (50%). Twenty-eight patients were exocrine insufficient (70%), of whom 19 used pancreatic enzymes. Vitamin A, D, E, and K deficiencies were present in 3, 53, 10, and 63% of patients, respectively. Osteopenia and osteoporosis were observed in 45% and 10% of patients. A decreased BMD was more frequently observed than expected, based on reference data, even in exocrine sufficient patients.

CONCLUSIONS

Deficiencies of fat-soluble vitamins and a decreased BMD are frequently present in chronic pancreatitis, even in exocrine sufficient patients. Consequently, all patients with chronic pancreatitis should be routinely screened for fat-soluble vitamin deficiencies and a decreased BMD.

HPLC Method for Plasma Vitamin K1: Effect of Plasma Triglyceride and Acute-Phase Response on Circulating Concentrations

Background: The plasma concentration of vitamin K1 (phylloquinone) is the most reliable index for assessing vitamin K status. Our aim was to analytically validate an HPLC method for quantifying phylloquinone in plasma and to examine the effect of plasma triglyceride concentration on the phylloquinone reference interval. We also examined the effect of acute-phase response on phylloquinone concentration in plasma.

Methods: Phylloquinone was extracted from fasting plasma samples by deproteinization and C18 solid-phase extraction, separated by reversed-phase HPLC, and detected fluorometrically after postcolumn reduction with a platinum catalyst. We synthesized a novel internal calibrator, docosyl naphthoate.

Results: The recovery of phylloquinone was >90%. Between-run imprecision was 8.7%–9.0%, and within-run imprecision was 3.8%–7.0%. The linearity was up to 44.8 nmol/L, limit of detection 0.08 nmol/L, and limit of quantification 0.14 nmol/L. The correlation between plasma phylloquinone and triglyceride concentrations was r = 0.7 in the reference population. The 95% reference interval for the phylloquinone:triglyceride ratio was 0.20 to 2.20 nmol/mmol. Plasma concentrations of C-reactive protein were significantly increased, whereas triglyceride and phylloquinone but not the phylloquinone:triglyceride ratio were transiently decreased >50% after surgery.

Conclusion: Phylloquinone population reference intervals should be expressed as a ratio of the triglyceride concentration. Phylloquinone concentrations in plasma are decreased in acute-phase response and, unless corrected for plasma triglyceride concentration, are unlikely to be a reliable index of vitamin K status.

Imaging of the central nervous system in suspected or alleged nonaccidental injury, including the mimics

Because of the widely acknowledged controversy in nonaccidental injury, the radiologist involved in such cases must be thoroughly familiar with the imaging, clinical, surgical, pathological, biomechanical, and forensic literature from all perspectives and with the principles of evidence-based medicine. Children with suspected nonaccidental injury versus accidental injury must not only receive protective evaluation but also require a timely and complete clinical and imaging workup to evaluate pattern of injury and timing issues and to consider the mimics of abuse. All imaging findings must be correlated with clinical findings (including current and past medical record) and with laboratory and pathological findings (eg, surgical, autopsy). The medical and imaging evidence, particularly when there is only central nervous system injury, cannot reliably diagnose intentional injury. Only the child protection investigation may provide the basis for inflicted injury in the context of supportive medical, imaging, biomechanical, or pathological findings.

Vitamin K status among children with cystic fibrosis and its relationship to bone mineral density and bone turnover

OBJECTIVE

The aim of this study was to assess vitamin K status in an unselected population of children with cystic fibrosis (CF) and to investigate any vitamin K effect on bone turnover and bone mineral status.

METHODS

Children > or =5 years of age who were attending the CF unit were invited to enter the study. Fasting blood samples were analyzed for levels of vitamin K1 and prothrombin produced in vitamin K absence; total, undercarboxylated, and carboxylated osteocalcin (OC); and bone-specific alkaline phosphatase and procollagen I carboxy-terminal propeptide (bone formation markers). Levels of N-telopeptide and free pyridinoline and deoxypyridinoline (bone breakdown products) were measured in urine samples. Bone mineral density and bone mineral content were measured at the lumbar spine and for the total body with a GE Lunar Prodigy densitometer. Statistical analyses were performed with Minitab version 9.1.

RESULTS

One hundred six children entered the study. Sixty-five of 93 children (70%) from whom blood samples were obtained showed suboptimal vitamin K status, on the basis of low serum vitamin K1 levels, increased prothrombin produced in vitamin K absence levels, or both abnormalities. Vitamin K1 levels showed a significant negative correlation with undercarboxylated OC levels but showed no significant correlation with any marker of bone turnover or measurement of bone mineral status. Undercarboxylated OC levels were correlated significantly with bone turnover markers, which themselves showed a significant negative correlation with measurements of bone mineral density and content. There were no significant correlations between carboxylated or undercarboxylated OC levels and bone density measurements.

CONCLUSIONS

Vitamin K1 deficiency is common among children with CF, and routine supplements should be considered. Through its role in the carboxylation of OC, vitamin K deficiency may be associated with an uncoupling of the balance between bone resorption and bone formation. A cause-effect relationship between vitamin K deficiency and low bone mass has not been proved.

Determination of the urinary aglycone metabolites of vitamin K by HPLC with redox-mode electrochemical detection

We describe a method for the determination of the two major urinary metabolites of vitamin K as the methyl esters of their aglycone structures, 2-methyl-3-(3'-3'-carboxymethylpropyl)-1,4-naphthoquinone (5C-aglycone) and 2-methyl-3-(5'-carboxy-3'-methyl-2'-pentenyl)-1,4-naphthoquinone (7C-aglycone), by HPLC with electrochemical detection (ECD) in the redox mode. Urinary salts were removed by reversed-phase (C18) solid-phase extraction (SPE), and the predominantly conjugated vitamin K metabolites were hydrolyzed with methanolic HCl. The resulting carboxylic acid aglycones were quantitatively methylated with diazomethane and fractionated by normal-phase (silica) SPE. Final analysis was by reversed-phase (C18) HPLC with a methanol-aqueous mobile phase. Metabolites were detected by amperometric, oxidative ECD of their quinol forms, which were generated by postcolumn coulometric reduction at an upstream electrode. The assay gave excellent linearity (typically, r2 > or = 0.999) and high sensitivity with an on-column detection limit of < 3.5 fmol (< 1 pg). The interassay precision was typically 10%. Metabolite recovery was compared with that of an internal standard [2-methyl-3-(7'-carboxy-heptyl)-1,4-naphthoquinone] added to urine samples just before analysis. Using this methodology, we confirmed that the 5C- and 7C-aglycones were major catabolites of both phylloquinone (vitamin K1) and menaquinones (vitamin K2) in humans. We propose that the measurement of urinary vitamin K metabolite excretion is a candidate noninvasive marker of total vitamin K status.

Beyond deficiency: potential benefits of increased intakes of vitamin K for bone and vascular health

Vitamin K is well known for its role in the synthesis of a number of blood coagulation factors. During recent years vitamin K-dependent proteins were discovered to be of vital importance for bone and vascular health. Recommendations for dietary vitamin K intake have been made on the basis of the hepatic requirements for the synthesis of blood coagulation factors. Accumulating evidence suggests that the requirements for other functions than blood coagulation may be higher. This paper is the result of a closed workshop (Paris, November 2002) in which a number of European vitamin K experts reviewed the available data and formulated their standpoint with respect to recommended dietary vitamin K intake and the use of vitamin K-containing supplements.

Assessment of vitamin K deficiency in CF—how much sophistication is useful?

BACKGROUND

Due to maldigestion of dietary lipids, fat soluble vitamins are prone to malabsorption in cystic fibrosis (CF) patients with pancreatic insufficiency (PICF). Routine supplementation of vitamin K(1) in PICF is presently subject of discussion.

METHODS

Serum vitamin K, prothrombin time, PIVKA-II ('liver marker', by two different ELISAs), hydroxyapatite binding capacity (HBC, 'bone marker') and ApoE genotypes were measured in 32 PICF patients (age: 7 months to 25 years) with (PICFK) or without (PICFN) oral vitamin K(1) supplementation, all receiving lipase supplementation, and in 18 healthy controls (C).

RESULTS

PIVKA-II was positive only in 4/7 PICFN. HBC medians of all groups were 57-60%. HBC values of PIVKA-II positive patients were below HBC median of their group. There was no correlation between HBC and PIVKA-II. There was no correlation between prothrombin time and other measurements. HBC medians with regard to ApoE were ApoE2/3 (62.9%)>ApoE3/3 (57.6%)>ApoE3/4+ApoE4/4=(56.65%).

CONCLUSIONS

Vitamin K deficiency of liver or bone may occur independently. Prothrombin time is an insensitive marker. Individuals with ApoE4 allels might be more susceptible to osteopenia. As high expenditures are necessary to detect patients at risk, routine vitamin K supplementation for all PICF patients appears appropriate.

Bone disease in primary biliary cirrhosis: independent indicators and rate of progression

BACKGROUND/AIMS

To identify indicators of osteoporosis and to determine the rate of bone loss in patients with primary biliary cirrhosis (PBC).

METHODS

Bone mineral density of the lumbar spine and hip was measured at annual intervals over 7 years of follow-up in 176 patients with PBC.

RESULTS

Osteoporosis (t-score below -2.5) was found in 20% of patients and occurred 32.1 times more frequently in patients with PBC than expected. Patients with histologic stage 3 or 4 disease had a 5.4-fold increased risk of osteoporosis compared to patients with stage 1 or 2. Age, body mass index, advanced stage (3 or 4), and history of fractures were the only independent indicators of osteoporosis. After 3 years of follow up, the rate of bone loss in patients with stage 1 or 2 increased and equaled that seen in patients with stage 3 or 4. Serum bilirubin level was the only variable independently associated with the rate of bone loss over time.

CONCLUSIONS

Severity of the liver disease contributes significantly to the severity of bone disease in PBC. PBC patients who are older, thinner and have more advanced liver disease may have the most benefit from bone density measurements and treatment for their osteoporosis.

Calciphylaxis associated with cholangiocarcinoma treated with low-molecular-weight heparin and vitamin K

Calciphylaxis is a rare disorder of small-vessel calcification and cutaneous infarction associated with chronic renal failure. Rare cases of calciphylaxis not associated with chronic renal failure have been reported with breast cancer, hyperparathyroidism, and alcoholic cirrhosis. To our knowledge, we report the first case of calciphylaxis without chronic renal failure associated with cholangiocarcinoma and the first attempt to treat calciphylaxis with vitamin K. A 56-year-old woman presented with necrotic leg ulceration. She was treated initially with low-molecular-weight heparin, with no effect. A coagulation work-up showed vitamin K deficiency. During vitamin K therapy, the patient had fulminant progression of the calciphylaxis. She died, and an autopsy showed metastatic cholangiocarcinoma. Thrombosis and protein C deficiency have been implicated in the pathophysiology of calciphylaxis. Functional protein C deficiency may be one of several factors contributing to the development of calciphylaxis. Vitamin K therapy was ineffective in our patient and may have been detrimental.

Japanese fermented soybean food as the major determinant of the large geographic difference in circulating levels of vitamin K2: possible implications for hip-fracture risk

Increasing evidence indicates a significant role for vitamin K in bone metabolism and osteoporosis. In this study, we found a large geographic difference in serum vitamin K2 (menaquinone-7; MK-7) levels in postmenopausal women. Serum MK-7 concentrations were 5.26 +/- 6.13 ng/mL (mean +/- SD) in Japanese women in Tokyo, 1.22 +/- 1.85 in Japanese women in Hiroshima, and 0.37 +/- 0.20 in British women. We investigated the effect of Japanese fermented soybean food, natto, on serum vitamin K levels. Natto contains a large amount of MK-7 and is eaten frequently in eastern (Tokyo) but seldom in western (Hiroshima) Japan. Serum concentrations of MK-7 were significantly higher in frequent natto eaters, and natto intake resulted in a marked, sustained increase in serum MK-7 concentration. We analyzed the relation between the regional difference in natto intake and fracture incidence. A statistically significant inverse correlation was found between incidence of hip fractures in women and natto consumption in each prefecture throughout Japan. These findings indicate that the large geographic difference in MK-7 levels may be ascribed, at least in part, to natto intake and suggest the possibility that higher MK-7 level resulting from natto consumption may contribute to the relatively lower fracture risk in Japanese women.

Adolescents: at increased risk for osteoporosis?

Perhaps the most important factor in the primary prevention of osteoporosis is the attainment of an optimal peak bone during adolescence. In addition to endogenous factors, such as genetic and ethnic background, environmental factors such as dietary habits, physical activity, and sex hormone therapy, influence the accretion of bone mass during this critical period of skeletal growth. First, calcium dietary intake in adolescents is generally well less than the current recommended RDA of 1200 mg/day. Multiple studies of children and adolescents have demonstrated increases in bone mass with dietary calcium supplementation. Second, regarding physical activity, the overall impression is that a moderate amount of particularly weight-bearing exercise has a positive impact on bone. There appears, however, to be a threshold of intensity of physical activity over which a negative impact on bone occurs, particularly when the exercise is of an anaerobic nature or occurring in very thin, amenorrheic participants. Third, previous research suggests that the various forms of hormonal contraception exert differing effects on bone mass in adolescents, with levonorgestrel implants and combined oral contraceptives may be associated with a more positive effect on bone mass compared with that observed with depot medroxyprogesterone acetate. From a clinical perspective, approaches to optimizing peak bone mass in adolescents would include increasing calcium intake, whether in the form of dairy products, fortified foods, or supplements as well as encouraging participation at a moderate level, in weight-bearing exercise. Last, in adolescents with extensive risk factors and predicted long duration of use, subdermal implants or combined oral contraceptives may be the optimal hormonal methods of birth control.